It has been widely known that utilizing a substance known as a carrier improves the performance of a detergent added to a fuel composition. The role of the detergent is to reduce the formation of intake valve deposits and injector deposits in internal combustion engines, as well as reduce or minimize the formation of deposits in the combustion chamber or actually remove existing deposits.
To enhance their ability to prevent or remove deposits, detergents have conventionally been added to fuels in conjunction with petroleum-based or synthetic carrier fluids. Petroleum-based carrier fluids include naphthenic and paraffinic base stock oils, and conventional synthetic fluids include low molecular weight polypropylenes, polyisobutylenes, poly-alpha olefins, esters, polyols, and polyalkyleneoxides. In recent years, the use of mineral oils as carriers has been reduced or eliminated due to their contributions to combustion chamber deposits.
While incorporating detergents and carriers in fuels has been effective in reducing intake valve deposits, in some instances, it can lead to an increase in combustion chamber deposits and/or valve sticking. It has been postulated that the carrier itself contributes to the formation of deposits, leading to strategies that minimize their use. Additionally, commonly used synthetic carriers are expensive, making it even more desirable to minimize their use. In the prior art (e.g., U.S. Pat. No. 6,800,103), solvent extracted and hydrotreated mineral oils have been proposed as alternatives to synthetic carriers; however, they have been targeted to have lower viscosity indexes to improve deposit control performance. Other prior art (e.g., U.S. Pat. No. 6,840,970) teaches the use of mineral oils and polyether carriers, but identifies mineral oils that are significantly more viscous than those of the presently claimed invention, and claims even higher viscosities as inherent in practicing that art. Based on the disclosures and teachings in the prior art, it is very unexpected that lower viscosity and high viscosity index hydrocarbon oils would demonstrate any benefit over previously utilized mineral oils.
Therein, a more effective and less costly carrier for fuel detergents would be a desirable contribution to the art.